Thread: Adjusting the speedometer for larger tyres?

The man with the radar gun (the "scientific" instrument) proved my GPS to be 100% accurate.
Regardless of what is used to "calibrate" the speedo, there is only one device that is deemed legal and accurate, but it costs (money and points) to find out.
Even allowing the "inconsistency" of GPS, (I have tested my 2 son's and mine side by side and found all 3 to read the same numbers, so not sure about inconsistent), the beauty is GPS doesn't discriminate when you change tyres and or wheel / tyre combos. Where as playing with the speedo is only effective for that specific combo?
And let's be honest the few Ks not recorded (or added) to the odo over time isn't going to matter. Even the maths for fuel consumption won't be measurably effected.
But twr7cx asked the question, and the answer is available.

Interesting this...

I know my speedo is out, due to tyres.

Yesterday, I set the cruise to 105, the Nanocom was reading 115, but the speed check bridge on the highway between Melbourne and Ballarat said 109...

So, who to believe? Was I speeding, or was I a shade under the limit?

Originally Posted by wopac5

The man with the radar gun (the "scientific" instrument) proved my GPS to be 100% accurate.
Regardless of what is used to "calibrate" the speedo, there is only one device that is deemed legal and accurate, but it costs (money and points) to find out.
Even allowing the "inconsistency" of GPS, (I have tested my 2 son's and mine side by side and found all 3 to read the same numbers, so not sure about inconsistent), the beauty is GPS doesn't discriminate when you change tyres and or wheel / tyre combos. Where as playing with the speedo is only effective for that specific combo?
And let's be honest the few Ks not recorded (or added) to the odo over time isn't going to matter. Even the maths for fuel consumption won't be measurably effected.
But twr7cx asked the question, and the answer is available.

You also live in Karratha Not a lot of tunnels or Tall buildings to cause canyoning of the GPS signal

Truspeed units have a 2 position switch...

Mine is calibrated to 33's on pos A and 35's on pos B...
I can also fine tune the calibration at any time...

As for trusting Police radar to be calibrated... I have fought a few fines in court over the years and won....

BTW - My max S.O.G on my gps tells me my Td5 has recorded a top speed of 206km/h and traveled a distance of just shy of 4000km on a tank of fuel... Depending on the Birds location, and surrounding influence even the best units can be erratic...

But again - If one wants to run O'Size tyres AND be legal... One must physically alter the speedo. The Truspeed unit meets requirements and allows for 2 sets of different diameter tyres to be used with the flick of a switch.

If you have a Nanocom Evolution, you can calibrate the speed reading it gives out.
In the imstrument mode, scroll right to the end and select the settings menu which will give you the coolant alarm setting and road speed option.
I'm running 245/70 16 which give me a reading on the speedo of about 4k's under true speed.
Think I have mine set to about 0.95% to correct it but haven't run it against the GPS yet to check.

Andrew


Using Capitals, the difference between helping your Uncle Jack off a horse or helping your uncle jack off a horse...

Originally Posted by LOVEMYRANGIE

If you have a Nanocom Evolution, you can calibrate the speed reading it gives out.
In the imstrument mode, scroll right to the end and select the settings menu which will give you the coolant alarm setting and road speed option.
I'm running 245/70 16 which give me a reading on the speedo of about 4k's under true speed.
Think I have mine set to about 0.95% to correct it but haven't run it against the GPS yet to check.

Andrew

And the inevitable question.....can that be done on the ever so elusive V8, or is it just another "TD5 only" teaser??

Originally Posted by LOVEMYRANGIE

If you have a Nanocom Evolution, you can calibrate the speed reading it gives out.
In the imstrument mode, scroll right to the end and select the settings menu which will give you the coolant alarm setting and road speed option.

Does this only alter the speed reading on the Nanocom Evolution or does this method also alter the speedometer reading on the vehicles instrument cluster?

Just been Google-ing and came across this, the Yellow Box.

Works exactly the same as the Truspeed unit (from what I can see), other than it can only be used for one set of tyres at a time, ie, not able to switch from standard to oversized as the Truspeed does.
But that's OK for me as I only run one set anyway.

And the good news is, it's half the price!
Works out to AUD$102 with free international delivery to 1st Sept!
Other than the switchability between two sets of tyres like the Truspeed, I really can't see why this would be any more or less suitable for "fixing" the speedo.....

Cheers,

Originally Posted by twr7cx

Does this only alter the speed reading on the Nanocom Evolution or does this method also alter the speedometer reading on the vehicles instrument cluster?

Nanocom only. Actual setting is 1.05 for my tyre size. Spot on with GPS reading.


Using Capitals, the difference between helping your Uncle Jack off a horse or helping your uncle jack off a horse...